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authorJoe Perches <joe@perches.com>2014-01-27 17:07:14 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-01-27 21:02:40 -0800
commit2e702b9f6cba4eb87d90e2a2d425a1fc05eec803 (patch)
treeade4a3bcec477ced2780f1841e7c06f547effe84 /kernel
parenta19428e5c3f4f39c302cb97b847dfd23613145c1 (diff)
softirq: use ffs() in __do_softirq()
Possible speed improvement of __do_softirq() by using ffs() instead of using a while loop with an & 1 test then single bit shift. Signed-off-by: Joe Perches <joe@perches.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/softirq.c43
1 files changed, 22 insertions, 21 deletions
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 8a1e6e10489..ba79bbfe380 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -229,6 +229,7 @@ asmlinkage void __do_softirq(void)
struct softirq_action *h;
bool in_hardirq;
__u32 pending;
+ int softirq_bit;
int cpu;
/*
@@ -253,30 +254,30 @@ restart:
h = softirq_vec;
- do {
- if (pending & 1) {
- unsigned int vec_nr = h - softirq_vec;
- int prev_count = preempt_count();
-
- kstat_incr_softirqs_this_cpu(vec_nr);
-
- trace_softirq_entry(vec_nr);
- h->action(h);
- trace_softirq_exit(vec_nr);
- if (unlikely(prev_count != preempt_count())) {
- printk(KERN_ERR "huh, entered softirq %u %s %p"
- "with preempt_count %08x,"
- " exited with %08x?\n", vec_nr,
- softirq_to_name[vec_nr], h->action,
- prev_count, preempt_count());
- preempt_count_set(prev_count);
- }
+ while ((softirq_bit = ffs(pending))) {
+ unsigned int vec_nr;
+ int prev_count;
+
+ h += softirq_bit - 1;
+
+ vec_nr = h - softirq_vec;
+ prev_count = preempt_count();
- rcu_bh_qs(cpu);
+ kstat_incr_softirqs_this_cpu(vec_nr);
+
+ trace_softirq_entry(vec_nr);
+ h->action(h);
+ trace_softirq_exit(vec_nr);
+ if (unlikely(prev_count != preempt_count())) {
+ printk(KERN_ERR "huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n",
+ vec_nr, softirq_to_name[vec_nr], h->action,
+ prev_count, preempt_count());
+ preempt_count_set(prev_count);
}
+ rcu_bh_qs(cpu);
h++;
- pending >>= 1;
- } while (pending);
+ pending >>= softirq_bit;
+ }
local_irq_disable();